1. Field of the Invention
The invention relates to a structure employed in an inkjet printhead for externally and electrically connecting the inkjet printhead, and more particularly to bonding terminations of an inkjet printhead having an actuator, wherein the bonding terminations are formed on the surface of the actuator for allowing its electrical connection with a flexible flat cable for use in transmission of control signals.
2. Description of the Related Art
Various types of inkjet printheads are known which include an on-demand type. An example of a conventional inkjet printhead of an on-demand type is constructed, as disclosed in Japanese Patent Publication No. 2002-19102, etc., such that a cavity unit in the form of a laminate of a plurality of plates incorporates a plurality of pressure chambers arranged in two rows. The cavity unit is joined to an actuator (a piezoelectric actuator, for example) having a plurality of active areas (ink ejecting energy generation areas) corresponding to the respective pressure chambers.
Further, in this example, surface electrodes are arranged in rows on the upper face (surface) of the actuator at its both edges extending longitudinally. The surface electrodes function as bonding terminations corresponding to the active areas of the actuator, for use in application of voltage to the active areas.
Still further, in this example, the surface electrodes (bonding terminations) of the actuator are bonded to bonding terminations of a flexible flat cable for use in transmission of external control signals, in superposed relationship thereon.
In an example of an inkjet printhead disclosed in the aforementioned Japanese Patent Publication No. 2002-19102, the actuator is constructed with a plurality of first green sheets; a plurality of second green sheets; and a top plate, all of which are ceramic bodies each made up of a piezoelectric material, for example.
Each one of the first green sheets includes patterns for individual electrodes formed on the surface of each first green sheet. Each one of the second green sheets includes a pattern of a common electrode formed on the surface of each second green sheet. The top plate includes surface electrodes for individual connection and surface electrodes for common connection formed on the surface of the top plate.
In this example, for constructing the actuator operable for ejecting ink droplets, the first and second green sheets are alternately superposed on each other, resulting in a laminate thereof, and the top plate is superposed on the uppermost one of the laminated sheets. The ultimate laminate of the sheets and the top plate is pressed and fired.
In this example, during above process, the individual electrodes and the common electrodes are formed on the surfaces of the sheets.
Ones of the individual electrodes (on the sheets) corresponding in position to each other as viewed in a lamination direction of the sheets are required to be electrically connected together. Each one of the surface electrodes (on the top plate) for individual connection and one of the individual electrodes (on the sheets) which corresponds in position to each surface electrode as viewed in the lamination direction are required to be electrically connected together, as well.
Ones of the common electrodes (on the sheets) corresponding in position to each other as viewed in the lamination direction are required to be electrically connected together. Each one of the surface electrodes (on the top plate) for common connection and one of the common electrodes (on the sheets) which corresponds in position to each surface electrode as viewed in the lamination direction are required to be electrically connected together, as well.
For achieving the above electrical connection between the sheets and the top plate, these sheets and top plate are pierced to form the respective through holes piercing through the sheets and top plate thickness wise, and these through holes are filled with conductive paste, during the formation of the individual electrodes and the common electrodes on the surfaces of the sheets.
These individual electrodes and common electrodes and the surface electrodes conductive thereto are formed by applying Ag (Silver)-Pd (Palladium)-based conductive paste onto the sheets and the top plate by a screen printing technique.
Another example of a conventional inkjet printhead is disclosed in Japanese Patent Publication No. HEI 11-147311. In this example, a flexible flat cable is constructed with a laminate of a plurality of substrate layers each having a wiring pattern formed on a single face thereof.
In this example, at least one of the plurality of substrate layers is pierced to form through holes via which the wiring patterns of other ones of the plurality of substrate layers behind the at least one substrate layer are exposed. On the exposed portions of the wiring patterns, there are formed bump electrodes (bonding electrode areas) which are bonded to surface electrodes of an actuator. These bump electrodes are typically made up of solder alloy which is softened and melted by heat.